1. Field of the Invention
The present invention relates to an ink jet recording apparatus for recording characters and images by discharging fine ink droplets onto a sheet, an OHP sheet, a cloth, or other recording medium. Particularly, the invention relates to an ink jet recording apparatus in which at least either one of a recording head and an ink tank is detachably installed on a carriage.
2. Related Background Art
There has been known an ink jet recording apparatus for recording by discharging fine ink droplets. This apparatus is advantageous over the apparatuses of other types because of its higher recording speed, easier recording in color, capability of recording not only on a regular sheet, but also on a cloth or other media, a lesser noise, and a higher quality among other features.
In general, the recording head of an ink jet recording apparatus has ink discharging ports of one to approximately 200 or 1,000 to approximately 2,000 in order to record on the entire recordable area, while allowing the head to scan a recording medium correlatively. The main scan is such that the carriage on which the recording head is mounted reciprocates to scan for the correlative movement. The subscan is such that a recording medium is scanned in one way in relation to the recording head. Here, the recording head mounted on the carriage is arranged detachably from the carriage or an ink tank which contains ink to be supplied to the recording head is arranged detachably from the recording head.
In the former arrangement, the recording head is replaced with a normal one for use if any malfunction takes place in the head or replaced with a new one completely when ink is finished in case of a recording head being arranged integrally with an ink tank.
In the latter arrangement, only the ink tank can be replaced with a new ink tank for use while the recording head remains unchanged when ink is finished. However, since the head or the ink tank or both are detachably mounted on the carriage, whether or not the recording head or the ink tank is installed correctly must be examined manually by the user or automatically by the apparatus itself for confirmation when executing a recording operation.
An examination of the kind by a user tends to be incomplete, while the automatic examination by a recording apparatus requires a sensor on the carriage. The sensor should be capable of transducing each event of the installation of a recording head or an ink tank into electrical signals, and transmitting them to the main body of the recording apparatus through flexible cables in order to make the required confirmation, and determine whether or not the installation is correctly carried out.
However, according to the above-mentioned conventional technique, there is a need for a considerable size of space for the arrangement of the flexible cables, which tends to make the size of the apparatus larger inevitably. Also, the use of durable cables results in a higher cost. Therefore, it is advisable to avoid any provision of flexible cables for the transmission of the electrical signals or it is advisable to minimize the number of cables for this transmission.
Also, if a sensor must be mounted on the carriage, the weight of the movable unit becomes heavier that much, necessitating the power of the motor for driving the carriage to be increased accordingly. Further, it take a longer time for the carriage to arrive at a constant speed. As a result, not only the recording speed is reduced, but also, a problem is encountered in that the apparatus should be made larger to the extent that the traveling distance of the carriage is made longer.
Also, among such ink jet recording apparatuses, there has been known an apparatus which is arranged to detachably install an ink cartridge in the main body of the apparatus or on a carriage as a source of ink supply so that the provision of ink can be made easily along with the consumption of ink for recording. An ink cartridge of the kind is replaced manually by the operator for use.
Further, there has been known an apparatus which is arranged to provide a function to prompt the operator to replace ink cartridges by detecting the ink remains when such an ink cartridge as above is used.
However, in the above-mentioned ink cartridge, it is technically difficult to detect the ink remains exactly. Also, the costs are extremely high if such a detection should be adopted. With a view to solving the problem, therefore, a method is proposed for detecting the ink remains in such a manner that the number of ink discharges from the head is counted, and the counted number is stored in a memory arranged in the main body of the apparatus, thus giving a warning when the stored number reaches a predetermined number of ink discharges. To effectuate this method, it is also necessary to reset the counter arranged for storing the counted number of ink discharges in the main body of the apparatus each time the ink cartridge is replaced. In this case, a switch and a detector for detecting the attachment and detachment of an ink cartridge must be provided. If the required resetting should be carried out by switching, it results not only in an additional cost, but also, in the operations imposed up the operator to execute such as depressing a start key and a reset key in addition to the replacement of the ink cartridges itself. This requires a considerable amount of work on the part of the operator. Also, the cost is inevitably increased by the additional provision of the detector.
Moreover, the flow of ink in the ink jet head or in the ink supply pipe should be interrupted when the ink cartridges are replaced. It is then necessary to exercise an extra suction from the ink discharge surface in order to fill ink in the ink passages up to the ink discharge ports.
As described above, there is a need for resetting the counter as well as exercising the extra suction when ink cartridges are replaced in a conventional ink jet recording apparatus. Also, it is necessary to detect whether or not the ink cartridge is installed correctly before these extra operations are performed.
Here, in a thermal transfer serial printer, it has been known traditionally that a structure is arranged for detecting the position of a carriage, the information regarding an ink ribbon cassette, and the end of the ink ribbon in it by use of an optical sensor provided in the home position for detecting a discriminating portion given to the carriage, a discriminating portion given to the ink ribbon cassette, and a window arranged for detecting the end of the ink ribbon (as disclosed in Japanese Patent Laid-Open Application No. 62-60680, for example).
In the thermal transfer printers, there is no possibility that the thermal head is damaged even if no ink ribbon cassette is mounted on the carriage or a printing is erroneously carried out in a state where the ink ribbon in the ink ribbon cassette is used up.
In an ink jet recording apparatus, however, there are some cases where the recording head itself should be replaced if the recording head is driven without mounting an ink cartridge or with an ink cartridge but having no ink in it (or with an ink tank which is formed with a recording head to provide an integrated unit, but having no ink in it), because the air and bubbles are mixed in the fine ink discharge ports or ink passages, thus inviting the disabled discharge of ink from the recording head. Also, in a recording head which discharges ink by use of thermal energy, the heater units may be damaged due to excessive heat in such cases. Therefore, in an ink jet recording apparatus, a technique required for detecting the presence or absence of an ink cartridge on a carriage or of the ink remains in the cartridge is vital to the life of the recording head. Particularly, in consideration of the current technical tendency which results in more frequent replacements of ink containers because of the prolonged life of the head itself, necessitating the replacement of the ink containers more often or in the adoption of a smaller ink container along the miniaturization of the apparatus itself, which also necessitates the replacement of the ink containers more often, the above-mentioned detection technique becomes increasingly more important in recent years.